The present invention relates generally to electrical connectors terminating cables that include twisted and shielded pairs of conductors, and relates in particular to a strain relief device for an electrical connector for high frequency data signals.
Electrical shielded data connectors are commonly employed to terminate signal-carrying, jacketed, multi-connector electrical shielded cables. Such cables are often used to connect various components of a data communication system. Each such data connector has a connector housing which supports a plurality of insulation displacement contacts (IDC). The individual conductors of the multi-conductor cable are terminated by the contacts for electrical connection. The jacketed cable extends past the connector housing to another component of the system, thereby creating a strain at the point where the cable leaves the housing.
Interconnection depends upon a good termination of the conductors of the cable with the contacts. Consequently, it is necessary to ensure that any strain placed on the jacketed cable is not transmitted to the contact termination. Such a strain could dislodge one or more of the conductors from the contacts, which would result in failure of the connector. Also, good electrical contact between the connector housing and the cable shielding must be ensured in order to provide a smooth transition of impedance. The cable shielding and the connector shielding, when assembled together, must be as close as possible to a metallic tube, with as little leakage as possible. Adequate pressure of the strain relief on the cable shield ensures good electrical contact; unfortunately, too much pressure on the cable bends it out of shape, degrades its transmission performance, and runs the risks damaging the conductors.
The prior art teaches a wide variety of strain relief devices. For example, U.S. Pat. Nos. 5,895,292, 5,766,040, and 6,077,122 show techniques for supporting jacketed cables in connectors. However, these prior art devices include so many parts that they are difficult to assemble. Also, none adequately accommodates a wide range of cable sizes, and none ensures a good electrical continuity of the shield without incurring the risk of over-stressing the cable""s conductors. Furthermore, these prior art devices may not protect against both inward and outward movement of the cable in the connector, and may not minimize undesired high-frequency, common-mode voltage induced between the connector housing and the cable shield.
The aforementioned problems are partially solved by the connector described in U.S. Pat. No. 5,445,538, which includes a connector housing defining a first bounded opening to permit passage of the cable. The cable strain relief device includes first and second hermaphroditic strain relief members for securing the cable. The first strain relief member is fixedly positioned within the housing, and the second strain relief member is movably supported with respect to the first strain relief member. The first and second strain relief members define a fully bounded opening surrounding the cable. The first and second strain relief members are movable so as to reduce the size of the seconded bounded opening for securing the cable by friction. Unfortunately, in order to obtain a good tightness resulting in a good electric contact, especially in the direction perpendicular to the direction of moving the second strain relief, it is necessary to tighten this relief member to a maximum, thereby incurring the risk of distorting the cable and finally crushing it.
Accordingly, an object of the invention is to provide a strain relief device for an electrical connector for high frequency data signals which ensures proper grip of the cable, results in a good 360xc2x0 seal, and does not deform or damage the cable so as not to degrade its electrical performance characteristics.
The invention includes a strain relief device for clamping an electrical connector designed to be interconnected to another connector of the same type so as to connect two cables. The two cables contain at least one twisted pair for transmitting very-high-frequency differential data signals. The conductors of the pair are connected in a connection block by Insulation Displacement Contacts (IDC) to contact blades, which are adapted to ensure contact in an interface block with the corresponding contact blades of the other connector. The device comprises two guillotines sliding in side grooves of the connection block. The side edges of the guillotines form a 90xc2x0 angle between them and a 45xc2x0 angle in relation to the direction of movement of the guillotines during the clamping operation, such that the side edges of both guillotines form a diaphragm when they approach one another, thereby ensuring a 360xc2x0 seal that prevents the cable from being deformed or damaged.